Archive labelled iPhone XS from Apple, a 962 KB RAR whose name does not reveal what is inside. At this size it could hold a schematic, a boardview, or reference diagrams rather than firmware, so extract it and inspect the files before relying on them. Repair technicians use such material to locate components, trace power lines and data signals, and find test points on the logic board. Boardview formats need a dedicated viewer, while PDFs open in any reader. Confirm that the board revision in the documents matches the device on the bench.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @schematic_mobiles. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.